Some word processing operations take significant amounts of time to complete. One such example is the adjustment of the beginning and end boundaries of document text information. To readjust the boundaries, the text editor reads the entire document from beginning to end and recomputes the beginning and ending boundaries. Other examples of time consuming operations are the printing of documents and the sorting of names and addresses on a mailing list.
In each of the above examples, word processing equipment without background processing capability must wait for the time consuming operation to be completed before another operation can be commenced. Thus the keyboard, which is central to a word processing system, can not be utilized during these operations. To solve these problems, word processing equipment have included background processing capability. The objective is to allow the keyboard to be utilized while the time consuming operation takes place in a background mode. However, prior word processing equipment had only a limited background capability usually associated with a specific tasks such as printing or pagination and none other. This is because of the need to keep the invocation of the background processing relatively simple for a user.
U.S. Pat. No. 4,191,956 granted to Groothuis, for example, discloses a foreground memory with a capacity of one page of text and a background memory with serial submemories connected in parallel, each submemory containing part of a character, so that together the submemories contain the relevant character within a series of characters. The characters become serially available on the outputs of the submemories for transfer to the foreground memory.
U.S. Pat. No. 4,198,685 granted to Corwin et al discloses a text editing system with the capability to select a sequence of signals from text storage and store it into special condition storage. Thereafter the system responds to a recall signal to disable the keyboard, retrieve the stored sequence, and operate according to it.